Hot melt adhesive composition containing a branched elastomeric copolymer

ABSTRACT

A hot melt adhesive composition comprising, in parts by weight, about: A. 100 PARTS OF PETROLEUM WAX, B. 40 TO 200 PARTS OF A TACKIFYING RESIN, AND C. 15 TO 100 PARTS OF A BRANCHED ELASTOMERIC COPOLYMER OF ETHYLENE, AT LEAST ONE C3 to C18 alpha-olefin, at least one direactive nonconjugated diene, and optionally at least one mono-reactive nonconjugated diene; said copolymer having a Mooney viscosity of about 10 to 70.

UNITED STATES PATENTS 4/1960 Gresham 260/28.5 A

0 United States Patent 91 [11] 3,821,143 Cluff et al. June 28, 1974 [54]HOT MELT ADHESIVE COMPOSITION 3,220,966 11/1965 Flanagan 260/27CONTAINING A BRANCHED 3,321,428 5/1967 Tordella 260/28.5 A

ELASTOMERIC COPOLYMER [75] Inventors: Edward Fuller Cluff; AustinPrimary Exami' 1er Anan Liffberman Mathew Snow, Jr" both f AssistantExaminer-P. R. Mlchl Wilmington, Del. [73] Assignee: E. I. Du PontdeNemours and [57] ABSTRACT Company, Wilmington, Del. [22] Filed Mar 221973 A hot melt adhesive composition comprising, in parts by weight,about:

[21] Appl. No.: 343,683 a. 100 parts of petroleum wax,

b. 40 to 200 parts of a tackifying resin, and c. 15 to 100 parts of abranched elastomeric 260/28'5 260/27 copolymer of ethylene, at least oneC to C alphwolefina at least one direactive [58] Field of Search260/28.5 A, 2856322277 nonconjugated diene, and Optionally at least onemono-reactive nonconjugated diene; said copolymer having a Mooneyviscosity of about 10 [56] References Cited to 70 9 Claims, N0 DrawingsHOT MELT ADHESIVE COMPOSITION CONTAINING A BRANCIIED ELASTOMERICCOPOLYMER BACKGROUND OF THE INVENTION strate to form a coating thereon,placing a second substrate on the hot melt coating, and cooling theresulting laminate to a temperature below the melt temperature of theadhesive composition to form an adhesive bond between the substrates.

The art has often suggested inclusion of an elastomeric polymer in hotmelt adhesive compositions. Elastomeric ethylene/propylene dipolymersand terpolymers have been proposed, for instance, because of theirexcellent modulus and tensile properties and compatibility with otheringredients in the hot melt composition. Hot melts containing thesepolymers, however, have had too high a viscosity at the desired level ofelastomer content for use in many conventional adhesive applicators.

In case sealing, for instance, the hot melt adhesive is generallyapplied under pressure through a nozzle at relatively low shear. The hotmelt usually must have a viscosity in the order of 100 to 10,000centipoise at application conditions in order that adequate amounts ofadhesive to accomplish sealing will be applied within a reasonable time.Prior art hot melt compositions containing elastomericethylene-propylene copolymers have generally had viscosities much higherthan this range, such as 50,000 centipoise or higher, at thedelene-propylene have not found-acceptance for use in low viscosityapplications, such as case sealing, despite many other excellentproperties.

SUMMARY OF THE lNVENTlON It has now been found that hot melt adhesivecompositions containing, as an elastomeric component, a branchedcopolymer of ethylene, at least one C to C alpha olefin, at least onedireactive diene, and optionally at least one mono-reactivenonconjugated diene have a lower viscosity than hot melts heretoforeknown which contained a linear ethylene/propylene dipolymer or EPDMterpolymer.

Accordingly, this invention provides a hot melt adhesive compositioncomprising, in parts by weight:

a. 100 parts of petroleum wax,

b. 40 to 200 parts of a tackifying resin, and

c. to 100 parts of a branched elastomeric copolymer of ethylene, atleast one C to C alpha-olefin, at least one direactive nonconjugateddiene, and optionally at least one mono-reactive nonconjugated diene;said copolymer having a Mooney viscosity of about 10 to 70.

DESCRIPTION OF THE INVENTION The hot melt adhesive compositions of thisinvention possess the excellent physical properties of high modulus,high tear strength, and compatibility of ingredients characteristic ofhot melt compositions containing a linear ethylene/propylene copolymer.The melt viscosity is, however, substantially reduced.

Based on petroleum wax, these novel hot melt adhesive compositionscomprise, in parts by weight:

a. 100 parts of petroleum wax,

b. 40 to 200 parts of a tackifying resin, and

c. 15 to 100 parts of a branched elastomeric copolymer of ethylene, atleast one C to C alpha-olefin, at least one direactive nonconjugateddiene, and optionally at least one mono-reactive nonconjugated diene.

As used herein, the term petroleum wax refers to both paraffin wax andmicrocrystalline waxes as well as equivalent synthetic waxes.

Paraffin waxis a mixture of solid hydrocarbons derived from the overheadwax distillate fraction obtained from the fractional distillation ofpetroleum. After purification, the paraffin wax contains hydrocarbonsthat generally fall within the formula C H C H Paraffin wax is asubstantially colorless, hard, translucent material usually having amelting point of about 52 to C. Microcrystalline wax is obtained fromthe nondistillable still residues from the fractional distillation ofpetroleum. It differs from paraffin wax in having branched hydrocarbonsof higher molecular weights. It is considerably more plastic thanparaffin wax and usually has a melting point of about 66 to 93C. Alsouseful are synthetic waxes such as Fischer- Tropsch wax.

Use of tackifying resins in hot melt adhesives'is well known in the art,and conventional resins compatible with both the selected wax andbranched elastomeric copolymer can be used to advantage. By compatibleis meant that the resin should not part to form a separate phase whenthe composition is heated to form a melt. The tackifying resin should bepresent in the amount of about 40 to 200 parts, and preferably to 150parts per 100 parts of wax.

Representative tackifying resins which can be used with advantageinclude natural rosins such as gum rosin, wood rosin, and tall woodrosin; hydrogenated wood rosin; esters of natural rosins such as methyland glyceryl esters of wood rosins; and methylated paraffinic chainhydrocarbon resins. Particularly useful are the aliphatic petroleumhydrocarbon resins prepared by polymerizing olefinsand diolefins. Thesehydrocarbon resins generally have a Ring and Ball softening point offrom 10 to C. Commercially available resins of this type includesynthetic polyterpene resins, such as Wing-Tack 95 sold by GoodyearChemicals. Other commercially available resins are Betaprene" H resinssold by Reichold Chemical'Corporation.

Additional useful tackifying resins include hydrocarbon resins preparedby polymerizing fractions of crude oil, suchas Piccotac" resins sold byPennsylvania Industrial Chemical Corporation; and terprene polymershaving a ball and ring softening point of about 10 to 135C. Othertackifying resins will be known to those skilled in the art.

The branched elastomeric polymer is a copolymer of ethylene, a C to Calpha-olefin, and at least one di reactive nonconjugated diene. Bydireactive is meant that the diene will copolymerize with other monomerspresent during polymerization through both of its double bonds.Optionally, a monoreactive diene can be present during polymerization.By monoreactive is meant that only one of the diene double bonds willenter the polymerization reaction. These branched copolymers can beprepared by polymerizing the monomers in an inert solvent in thepresence of a coordination catalyst, as disclosed in Canadian Pat. No.855,774 to Campbell and Thurn.

Propylene is the preferred alpha-olefin, although other alpha-olefinssuch as l-hexene, l-butene, ldecene, and l-dodecene can be selected withadvantage. Representative direactive dienes copolymerized to introducebranching include monomers having two terminal'double bonds, such asl,4-pentadiene; 1,5- hexadiene and 1,7-octadiene. The direactive dienecan also be a strained-ring diolefin, such as the reaction product ofnorbornadiene-2,5 and cyclopentadiene, or

preferably 2,5-norbornadiene. Representative monoreactive dienes whichmay optionally be copolymerized include cycloaliphatic compounds such as5-ethylidene-2-norbornene,' 5-methylene-2- norbornene, and5-p'ropenyl-2-norbornene; and nonconjugated aliphatic diolefins such as1,4-hexadiene, l,9-octadiene, and the like.

Suitable branched copolymers have a Mooney viscosity ML l 4/l21C. ofabout to 70, and most preferably about 18 to 30. When the hot melt is tobe used in applications such as in case sealing, branched copolymershaving gel particles large enough to plug the nozzle orifice should beavoided. Gel content and gel particle size is conveniently reduced bydecreasing the quantity of direactive diene in the polymer.

When propylene is selected as the alpha-olefin, the branched polymergenerally contains about 40 to 80 percent by weight ethylene, about 0.01to 0.5 mole direactive diene per kilogram of copolymer, and optionallyabout 0 to 2 moles monoreactive diene per kilogram of copolymer. Thebalance is propylene. Preferred copolymers have about 70 to 74 percentby weight ethylene and about 0.1 to 0.3 mole direactive diene perkilogram of copolymer, with the preferred direactive diene being2,5-norbomadiene. Preferably, as in the case of 1,4-hexadiene, themonoreactive diene is present in about 0 to 6 percent by weight. Thebalance is propylene. 4

The branched copolymer should be present in at least about parts per 100parts of wax to achieve flexible bonding. Generally, additions in excessof 100 parts per 100 parts of wax will not increase performance of theadhesive composition. Preferably, the adhesive composition will containabout 20 to 50 parts branched copolymer per 100 parts wax.

Minor amounts of thermal stabilizers such as antioxidants, and ofconventional adhesion promoters can be included in the adhesivecomposition to enhance physical properties. Polypropylene plasticizercan be used in placeof a part of the branched copolymer to furtherreduce viscosity of the hot melt adhesive without undue loss of physicalproperties. Extender oils, such as a paraffinic petroleum oil, can beused to like advantage, if desired.

The hot melt adhesive composition is conveniently prepared in anagitated, oil-jacketed kettle heated at about 163 to 191C. First the waxand resin are introduced and allowed to melt. Then the branched polymeris added and mixing is continued until it dissolves. Finally, theoptional adhesion promoters and antioxidants are added. When theresulting stirred mixture is homogeneous, it is poured and allowed tocool.

Alternatively, an internal mixer, such as one having a sigma blade, canbe employed. In this case the polymer is added before the wax. Theoptional adhesion promoters and antioxidants are then introduced. Atleast 30 minutes of mixing is generally required to ensure a homogeneousmelt.

When the hot melt composition is to be used in case sealing, it isgenerally desired that the composition have a viscosity of about 100 to10,000 centipoise as measured at 190C. with an RTV Brookfield Thermoselviscometer using a No. 21 spindle at 20 rpm. Melt viscosity is adjustedfor the particular branched copolymer and application equipment byvarying the ratio of wax and tackifying resin to branched polymer withinthe limits hereinbefore prescribed. In general, the hot melt viscosityis decreased by an increase in proportions of wax or tackifying resin.

Hot melt compositions of this invention having a viscosity higher thanabout 10,000 can be used in other adhesive applications, such as thoseemploying a wheel or gear applicator. To increase viscosity of the hotmelt composition, the quantity of branched copolymer relative to wax andtackifyingresin is increased.

In the examples that follow, all parts and percents are by weight unlessotherwise indicated. Viscosity measurements are as taken with an RVTBrookfield Thermosel viscometer using a No. 27 spindle unless otherwiseindicated. Ring and Ball softening points are determined following theprocedures of ASTM E-28-5 8T.

EXAMPLE 1 A. The synthetic resin used is a polyterpene resin having aRing and Ball softening point of 100 5C., sold as Wingtack by GoodyearChemicals. The petroleum wax used is a fully refined paraffinic waxhaving a melt point of 61C. (ASTM Test Method D-87). The branchedelastomeric tetrapolymer used has the following monomer unitcomposition: ethylene, 72.75%; propylene, 23%; 2,5-norbornadiene, 0.15%;and 1,4-hexadiene, 4.1%. This tetrapolymer has an inherent viscosity of1.25 at 30C. (measured on a solution of 0.1 gram of tetrapolymer in ml.of tetrachloroethylene), and a Mooney viscosity (ML l 4/l2lC.) of 19.

A 2-gallon agitated, oil-jacketed mixing kettle is heated to about 177C.and charged with 100 parts of Wingtack 95 and 100 parts of refinedparaffinic wax. When these components have melted, 40 parts oftetrapolymer are slowly added. When the resulting stirred mixture hasbecome homogeneous, it is poured and allowed to cool. For test purposes,a portion of the mixture is collected on a stainless steel tray, cooled,and cut into one-inch squares when solid. Typical results of viscositymeasurements are recorded in Table l.

TABLE 1 COMPOSITION PROPERTIES Ingredient Parts Ball and Ring SofteningPoint: 63-65C.

Branched Tetrapolymer 40 Tern C. I S indle S eed r m Viscosit c s 5653.".188 1' 1 I88 i353 276' 190 100 1275 B. For comparison, a hot meltadhesive composition about 2 to 6 seconds to distribute the beads onboth is prepared using the resin and wax and following the surfaces(compression section). Pressure is then reprocedures of Part A exceptthat a linear elastomeric moved. The paperboards are very satisfactorilybonded ethylene, propylene, 1,4-hexadiene terpolymer (72% together bythe adhesive. ethylene, 25.2% propylene, 2.8% 1,4-hexadiene; ML-

l 4/ 121C. of 60) is substituted for the branched tet- EXAMPLE 2-rapolymer. Typical results of testing are recorded in Table w M l lotmelt adhesive compositions are formulated using TABLE 2 COMPOSITIONPROPERTIES In redient Parts Ball and Ring Softening Point: 6578C. Emearlerpolymer 40 Tem C. S indle S eed m' Viscosit c s ax 17 2.5 49,500 'TZT177 5.0 48,700 190 5.0 37,000 204 5.0 24,250 204 I00 (l) )liscosity sohigh that no spindle speed above to rpm is suitable.

Comparison of Tables I and 2 shows that the hot the branchedtetrapolymer and procedures of Example melt adhesive compositioncontaining branched elastol and using a variety of fully refinedparaffin waxes and mertc tetrapolymer has an unexpectedly low viscosityresins. Viscosity measurements are taken on these in comparison tosimilar hot melt compositions concompositions at 190C. usinganumber 21spindle at 20 tam ng a linear elastomeric terpolymer. rpm. Results arerecorded in Table 3.

TABLE 3 Ingredient A B C D Branched tetrapolymer 40 40 40 40 Petroleumhydrocarbon resin" 100 Synthetic polyterpene resin I00 l00 100 MP. 3Fully refined 61C. I00 100 Paraffin C. I00 Wax 84C. Adhesion promoter2.0 2.0 2.0 2.0 2,6 Ditertiary butyl-4-methyl phenol 2.4 2.4 2.4 2.4Boric acid powder 2.4 2.4 2.4 2.4 Viscosity, cps 1945 I545 I867 2345 (1)Ring and Ball Softening Point ll9C.; Piccotac A, Pennsylvania IndustrialChemical Corporation.

(2) Ring and Ball Softening Point 100 5C.; Wing-Tack" 95, GoodyearChemicals.

(3) Melting Point, ASTM Test Method D-87.

(4) Maleic Anhydride Grafted Polyethylene; Epolene C-l6. EastmanChemical.

C. Bonding Corrugated Paperboard EXAMPLE 3 The hot melt adhesive Of PartA is placed in the reser- To demonstrate extensibility of the hot meltcompovoir of a Nordson'f Hot Melt Applicator Mark IV, sitions,polypropylene is added to ahot melt in the proheated to about 163 tol9lC.,.conveyed to a heated 6 portions shown in Table 4. Thepolypropylene has a nozzle tip, and propelled by air onto a corrugatedpapeak melting temperature of 157%C. as measured by perboard to formfour (4) heads of pencil width. A secdifferential scanning calorimetrywith a heating rate of 0nd corrugated paperboard is held against thefirst for l0 C./ min Thebranchedtetrapolymenwaxand tackifying resin areas identified in Example 1. Extended compositions B, C and D are testedfor Brookfield viscosity, Lap Shear Temperature and Peel Temperature.The same tests are conducted on nonextended compononconjugated diene perkilogram of copolymer, and about to 2 moles of a monoreactivenonconjugated diene per kilogram of copolymer, the balance of thecopolymer being propylene; said cosition A. Test results are recorded inTable 4. polymer having a Mooney viscosity of about to Peel temperatureis determined by applying a strip of 70. test adhesive, 3.2 mm. wide by0.005 mm. thick, on a h Composltlon of clalm 1 wherein the direactive30-16/ream (49 glm Kraft paper. A second sheet of dlene 1S th same paperi l d i di alignment i h h 3. The composit on of claim 1 wherein thedireactive first sheet and heat-sealed to it. Thebonded papers are 10(116116 flq cut, perpendicular to the bond line, into 2.54 cm. wide 7The composltlon of Claim 1 havlng a vlscoslty at strips. Duplicatebonded specimens are placed in an 190C of about to 9 oven with one freeend of the specimen attached to a 5- Th mposition of claim 4 comprisingabout: fixed support. A 100 g. load is suspended from the 100 P n ofPetroleum other free end. Tests are initiated at room temperature 15 2.100 to 140 parts of a tackifying resin; (24C.). The oven temperature isthen increased in 3. to 50 parts of a branched elastonieric copoly- 5C.increments at 5 min. intervals. The temperature at mer having a Mooneyviscosity of about 18 to which bond delamination occurs is specified asthe peel and containing about 0.1 to 0.3 mole direactive temperature.Lap Shear temperature is determined in nonconjugated diene per kilogramof copolymer. the same manner as. the Peel Temperature except 20 6. Thecomposition of claim 5 wherein the direactive that White Richford Blankcardboard (14 X 22 inch, 10 diene is 1,7-octadiene. ply) is used and thesheets are bonded at perpendicular 7. The composition of claim 5 whereinthe direactive a nm n 9ini$2rn9b2 aq 22- TABLE 4 COMPOSITION A B c DBranched Tetrapolymer 80 40 6O 80 Boric Acid 4.8 4.8 4.8 4.8 2,6Ditertiary butyl-4-methyl 4.8 4.8 4.8 4.8

phenol Maleic Anhydride Grafted Polyethylene 4.0 4.0 4.0 4.0Polypropylene 40 40 80 Wax 200 200 200 200 Tackif ing Resin 200 200 200200 Brook ield Viscosity, l90C..cps. I882 272 847 I865 Lap ShearTemperature, C. 70 7O 70 7| Peel Temperature 46 42 42 Table 4demonstrates that the hot melt composition 40 8. The composition ofclaim 5 wherein the branched n b extended Without adverse 0n ap Shearelastomeric copolymer contains about 70 to 74 percent or PeelTemperature. by weight ethylene, about 0.1 to 0.3 mole 2,5- We Claim:norbomadiene per kilogram of copolymer, up to 6 per- A hOt I Y U P lcomprlsmg, 45 cent by weight 1,4-hexadiene, the balance being propypartsby weight, about: 1

l. 100 parts of petroleum 9. The composition of claim 5 containing atleast one 40 o 200 Parts Of a i y g resin; and of polypropylene and anextender oil. 3. 15 to 100 parts of a branched elastomeric copolymercontaining about 40 to 80 percent by weight of ethylene about QOl to QSmole of a direactive

2. 100 to 140 parts of a tackifying resin;
 2. The composition of claim 1wherein the direactive diene is 2, 5-norbornadiene.
 2. 40 to 200 partsof a tackifying resin; and
 3. 15 to 100 parts of a branched elastomericcopolymer containing about 40 to 80 percent by weight of ethylene, about0.01 to 0.5 mole of a direactive nonconjugated diene per kilogram ofcopolymer, and about 0 to 2 moles of a monoreactive nonconjugated dieneper kilogram of copolymer, the balance of the copolymer being propylene;said copolymer having a Mooney viscosity of about 10 to
 70. 3. Thecomposition of claim 1 wherein the direactive diene is 1, 7-octadiene.3. 20 to 50 parts of a branched elastomeric copolymer having a Mooneyviscosity of about 18 to 30 and containing about 0.1 to 0.3 moledireactive nonconjugated diene per kilogram of copolymer.
 4. Thecomposition of claim 1 having a viscosity at 190*C. of about 100 to10,000.
 5. The composition of claim 4 comprising about:
 6. Thecomposition of claim 5 wherein the direactive diene is 1, 7-octadiene.7. The composition of claim 5 wherein the direactive diene is 2,5-norbornadiene.
 8. The composition of claim 5 wherein the branchedelastomeric copolymer contains about 70 to 74 percent by weightethylene, about 0.1 to 0.3 mole 2,5-norbornadiene per kilogram ofcopolymer, up to 6 percent by weight 1,4-hexadiene, the balance beingpropylene.
 9. The composition of claim 5 containing at least one ofpolypropylene and an extender oil.